COMPOSITES: PAST, PRESENT & FUTURE
Recycled carbon fiber: Its time has come
» The carbon fiber industry has changed a lot in the past 15
years. In 2000, the global market for carbon fiber was less than
20,000 MT. Now, it is greater than 60,000 MT per year, and forecasts indicate this will increase to between 100,000-140,000 MT,
annually, in the early 2020s. The impressive growth that we’ve
seen already — and that we expect to continue — puts a new
emphasis on the role of carbon fiber recycling in the development
of the industry.
The process from manufacturing carbon fiber to production of
finished components is wasteful; it is estimated that more than
30% of produced carbon fiber ends up as waste at some point in
the process. Where the carbon fiber composites industry most
differs from other industries that produce high proportions of
waste is that it
lacks an effective
recycling solution.
Impressive industry growth
This
is not to say
puts a new emphasis on
that we cannot
the role of carbon fiber
recycle carbon fiber.
recycling.
ELG Carbon Fibre is
one of several companies that have developed
cost-effective means of recovering carbon fibers from manufacturing waste and end-of-life components without significantly
degrading fiber properties. But there are significant barriers to
returning reclaimed fiber materials to the market.
To understand why, we need to briefly recap the current status
of recycled carbon fiber materials. Today, recycled products exist
in forms that are suitable for use by compounders (milled and
chopped fibers in powder or pellet form) and in composite layups
(nonwoven mats as dry fabrics as well as prepregs and SMC materials), as shown in Tables 1 (at right) and 2 (p. 8). However, the use
of these products outside of R&D projects is, thus far, very limited.
The major barrier that must be overcome is one faced by all
new materials — lack of knowledge about mechanical properties
and processing characteristics, and lack of large-scale demonstrators that prove the economic, technical and environmental justification for using these materials. Although there are a number of
projects that are addressing these issues, the push from the manufacturing side of the supply chain to find a solution to its carbon
fiber waste problem generally isn’t matched by a pull from the
supply chain’s design side to find ways of using recycled carbon
fiber products.
To date, the most successful demonstration of recycling has
been BMW’s (Munich, Germany) use of reclaimed carbon fiber
materials in its i3 and 7-Series models, in which manufacturing
waste from dry fiber processes has been converted into new
product forms and used in closed-loop recycling solutions. This
was greatly facilitated by the integrated supply chain that BMW
and SGL Group (Wiesbaden, Germany) established. If such
6
JULY 2016
Recycled fiber
supply base
The supply base for discontinuous milled and (left) chopped
fibers and longer fibers and
fiber forms is established and
growth-capable. The missing
piece is demand.
Source | ELG Carbon Fibre Ltd.
Comparison of Reinforced Thermoplastic Compounds
Reinforcement
Density
(gcm-3)
Flexural
Strength (MPa)
Young’s
Modulus (GPa)
30% Glass
Fiber
10% Virgin
Carbon Fiber
10% Recycled
Carbon Fiber
1.38
1.21
1.17
259
223
232
9.0
10.3
10.3
Table 1 Recycled CF in reinforced thermoplastic
compounds
Recycled carbon fiber exists in forms that are suitable for use by compounders
(milled and chopped fibers in powder or pellet form). Source | Albis (UK) Ltd.
integrated supply chains don’t become the norm in future, then it
is vital that all elements of a supply chain work closely together not
only to develop methods of recycling carbon fiber, but also to get
recycled carbon fiber products back into the supply chain.
Why should we do this? From an economic standpoint, recycled
carbon fiber products can reduce the cost of lightweighting, used
either on their own or in conjunction with virgin carbon fibers. In
fact, making lightweighting strategies affordable must be a primary
goal if we are to see increasing use of carbon fiber in high-volume
applications. If we address this challenge, then we can increase
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COMPOSITES: PAST, PRESENT & FUTURE
Properties of Recycled Carbon Fiber SMC
Reinforcement
40% Recycled Carbon Fiber
Density (gcm-3)
1.40
Tensile Strength (MPa)
370
Tensile Modulus (GPa)
33.3
Flexural Strength (MPa)
650
Flexural Modulus (GPa)
41.7
Tg (°C)
151
Table 2 Recycled carbon fibers in SMCs
Recycled carbon fibers also have been adapted in forms that can be used in sheet
molding coumpounds (SMCs). Source | ELG Carbon Fibre Ltd.
the total use of carbon fiber in these developing markets. From the
environmental standpoint, reducing waste and reusing materials
that have a high embedded energy, and which can be recycled in
an energy-efficient manner, is the right thing to do, from a social
responsibility point of view. It also is a legislative requirement in
some countries.
Finally, there’s the question of the growth forecasts for carbon
fiber. It has taken the industry 15 years to add 40,000 MT of carbon
fiber manufacturing capacity. If the demand forecasts are to be
believed, the next 40,000 MT of capacity must be added in the
next 5 years. Making use of high-cost materials that, today, are
consigned to landfill can be part of the solution to filling the anticipated gap between supply and demand.
In summary, a number of companies across the globe have
developed cost-effective solutions to carbon fiber recycling, and
an initial range of products now available for the compounding
and composites industries. The time is right for the industry to
work together, to move recycling from the fringes to its rightful
place as an integral part of the carbon fiber market. In doing so,
we improve the cost and the environmental footprint of our businesses, create additional and sustainable supply chains for critical
raw materials, and help the overall carbon fiber composites
industry grow.
ABOUT THE AUTHOR
Frazer Barnes is managing director of ELG Carbon Fibre Ltd.
(Coseley, Dudley, UK), part of the ELG Haniel Group, where he
is responsible for developing the business into a global leader
in carbon fiber recycling. Barnes started his career working for
SP Systems (now Gurit, Isle of Wight, UK), and more recently
worked in the UK, US and China for Cytec Engineered Materials (now Cytec
Solvay, Woodland Park, NJ, US), and at Hengshen Carbon Fibre (Jiangsu, China).
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